Reaction of hydroxyl radical with phenylpropanoid glycoside and its derivatives by pulse radiolysis.

The reaction of hydroxyl radical with 1 phenylpropanoid glycoside (PPG), cistanoside C, and its 3 derivatives: 1-0-beta-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-femloyl-glucose and 6-O-(E)-p-hydroxy-cinnarnoylglucose isolated from folk medicinal herbs was investigated by pulse radiolysis technique respectively. The reaction rate constants were determined by analysis of built-up trace of absorption at lambda(max) of specific transient absorption spectra of PPG and its derivatives upon attacking . OH. All four compounds react with . OH at close to diffusion controlled rate (1. 03 x 10(9)-19.139 x 10(9) L . mol(-1) . s(-1)), suggesting that they are effective . OH scavengers. The results demonstrated that the numbers of phenolic hydroxyl groups of PPG and its derivatives are directly related to their scavenging activities. By comparing the reaction rates of . OH with 1-O-beta-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-feruloyl-glucose or 6-O-(E)-p-hydroxy-cinnomoyl-glucose, it is evident that the phenylethyl group is more impofiant than phenylacryloyl group for scavenging . OH.